Dan's Data letters #66

Publication date: 13 October 2003.
Last modified 16-Jul-2012.

 

Degrees per what?

Which is better for a CPU cooler, a lower or higher C/W?

Steve

Answer:
Lower. The thermal resistance specification, in degrees per watt, tells you how much hotter whatever sensor's being used gets when the cooler has to deal with one more watt of heat. So if the thermal resistance is 0.6C/W, ten watts of heat will result in a temperature 6C above ambient, and a hundred watts will result in 60C above ambient.

Note that the positioning of the heat sensor can hugely vary the C/W figure. The sensor in my own CPU test rig is quite close to the heater element, so it tends to produce high numbers.

 

Dream the impossible input dream

I enjoyed reading your thoughts on the old IBM "clicky" keyboards. I completely agree with you on their many superior aspects. I am currently looking to purchase a new keyboard for myself, and I would absolutely love to get one that clicks like those old ones. Problem is, I also want it to be wireless. If I can't set something up that is both wireless and clicky, I'll have to go with non-clicky. You seem to know a lot about the various gadgets out on the market, so I thought you might have a good suggestion as to how I can achieve this goal.

Dave

Answer:
I don't think anybody makes a wireless 'board with proper keyswitches. PS/2 to USB converters exist, and so do USB to Bluetooth (or other R/F) converters, but you'd end up with a ridiculous amount of stuff strapped to your keyboard if you tried to do the trick that way, if you could make it work at all.

 

Fully imported

I was wondering whether parts bought overseas - the USA or other places - can be used in Aussie PCs?

Nick

Answer:
Sure they can. Not power supplies that expect 110 volt input, of course, but regular PC parts - motherboards, RAM, cards - are generally all fine. Modems and other comms devices may or may not be legal to use in Australia, but lots of people just use 'em anyway. The Australian government doesn't particularly care if you use an FCC-approved but not Australian-approved modem, as long as you're not selling the things.

Telstra will wreak Horrible Vengeance upon you if they find out you're not legit. The usual strategy for avoiding this is to not tell them.

 

RGB CCDs

What are your thoughts on the Foveon X3 full color image sensor?

(And the cameras that use it...)

I think this is a really good idea that doesn't seem to have taken off in the digital camera market.

Bill

Answer:
I talked about the X3 sensor back in this column. The situation hasn't changed; there's still exactly one X3-sensor camera, it's still the rather weird SD9 (Sigma lens mount, no JPEG mode, blah blah; review here), and the plain old mosaic-filter sensors are walking past it in resolution. The SD9's only up there with the six megapixel mosaic sensors for resolution, and they're almost consumer products now!

I don't know of any terrible problems with the X3 idea that mean that it, or some variant on it, couldn't end up being used by lots of cameras in a few years. But it's possible that we'll just keep using higher and higher resolution mosaic sensors. Yes, they've got lower chroma resolution than luma resolution, but so does the human eye, and we're generally pretty happy with it!

 

Dead drive #21863

After a recent trip to Sydney to see my family, I returned to a computer that worked - for one day. The next morning I turned my computer on it hung with a BSOD. The error was unmountable_boot_volume blah blah.

I tried the recovery console, CHKDSK /R seemed the best option, but it did sweet FA. I even tried formatting it (knowing that my recovery software normally gets most data back) but that has done nothing as well.

So now I give up and am asking you for some help.

Nathan

Answer:
Sorry, but you're not going to get any. My guess, given that you've already done the two things I would have tried first, is that the drive has failed. It happens. It doesn't happen very often any more, but it's not unheard of.

It's unlikely to be a "stiction" problem, since it was working the day before and stiction's practically unknown these days anyway, but it doesn't hurt to try twisting the drive in the axis of its platter axle, to spin the platters a bit. You could also try freezing it, as per this column. Frankly, though, I'd be surprised if it came back.

 

Madness!

I have a couple of old DOS games that will work in Windows, but when they hit a certain effect, go blammo. The games are "Shadow Warrior" and "Blood". The problem according to 3D Realms is that their special 3D sound effects when underwater, or in Blood using the damage reflection thing, blow up when the sound card is on anything over IRQ 9. I asked if there was any way to fix this, and was told in essence no, and that it sucked to be me.

This was not the most helpful answer I've ever gotten. It seems like it would be a simple matter to put an option for "no 3D sound"' in, if nothing else, or at least a bit of apology for the problem.

My Sound Blaster Live Value card refuses to run on anything other than IRQ 11. Even on a complete wipe and reinstall of Win98, it doesn't want to change. Is there any way to force it to use a different IRQ? The bootup listing of IRQs seems to have a hell of a lot of stuff on IRQ 11.

I'm using a Biostar M7VIF motherboard, and I've disabled the on-board sound and video. I've got a generic NIC, the SB Live Value, a ACR modem and an MSI 64Mb GeForce4 Ti4200 video card (with a two pound copper heat sink on it. I almost wanted to prop the thing up with a stick...)

Help?

StarChaser

Answer:
Indeed, this is a known problem.

This is also one of those situations where, after I put a letters page up, readers invalidate my reply by coming up with better solutions. Here those solutions are.

There does in fact exist a no-3D-sound patch (scroll down the page a bit) created by Build engine coder Ken Silverman. That's for Duke Nukem 3D and Shadow Warrior, and not any of the other multitudinous Build engine games, including Blood.

No problem, though; here you will find Blood sound patches, for both DOS and Windows.

And now, my irrelevant original answer, in small, shamefaced text:

The instructions provided in the FAQ won't work for you, because you have a modern PC with ACPI. Since you're running Win98, though, you may be able to restart, go into your BIOS setup program, disable ACPI, then reboot and actually have Windows work without a reinstall. It'll freak out utterly because everything will have changed addresses, and you may not end up with enough addresses to accommodate all of your hardware, but I think it'll all fit. The NT-series Windows flavours - Win2000, WinXP - need to be reinstalled if you disable or enable ACPI, but Win98 can survive it.

Once your computer's recombobulated itself (ideally, it should do it with no supervision, thanks to good old Plug and Play...), you ought to be able to change the sound card address, one way or another. If you can't change the card's address in its Properties, you'll be able to change it either by change the IRQ bound to each PCI slot in the BIOS setup, or by physically swapping the card into some other PCI slot, moving another card to take its place if necessary.

An alternative strategy is to run a PC emulator on your PC. Sounds nuts, but makes sense for people who want to test software that may do Awful Things to a system; you run an emulator with whatever specs you want (generally using a file on your hard drive as its "hard drive", and with other specs determined by the emulator software), and away you go. Emulators are slow, but a modern PC still has more than enough power to play old DOS games, provided you're running an emulator that can emulate compatible hardware.

VMware is the most popular PC-platform PC emulator, but for the money you'd probably do better to just buy an old PC and a keyboard/video/mouse switcher! It's free to evaluate for 30 days, though.

There's also Virtual PC, but it's a commercial product and currently unavailable. Bochs seems likely to work, but isn't as friendly. DOSBox won't do games until it supports protected mode, which the current version doesn't.

[UPDATE: It's been years since this page first went up, and DOSBox can now run a huge list of old games.]

You aren't necessarily going to need a whole-computer emulator, by the way; "virtual sound card" software like VDMSound (see also here) might be able to do the trick.

 

Flash feeding

I have some flashguns for my cameras, and I was wondering if using NiMH batteries in them (they take four AA's) will break anything.

The flashes come with very helpful notices suggesting that I use nothing but alkalines, but since they chew up electricity pretty quick, I was wondering if I would burn anything out by ignoring the warnings.

The two flashes are an Achiever 260AF and a Vivitar 283.

Mark

Answer:
It'll be fine. I don't know of any AA-powered flashes that don't work with NiCd and NiMH rechargeables, and a good thing too.

Here's one among many references.

 

Lead, valves and other oily stuff

In reference to this column's last letter - years ago, the mechanic I used to regularly take my car (a pretty tidy HR Holden) to for service actually stocked the little devices you are referring to!

All you had to do was place the little bugger somewhere in your fuel line, and then your old car could use unleaded fuel.

How does it work, you ask? Well the principle was quite simple; the thing was made out of tin (I think) and this tin would go into the fuel somehow. Don't ask; I don't know the specifics! So, replacing tin for lead, your engine is protected from wear. No idea how well it worked, however I do know it worked (I asked, the mechanic told me he had installed a couple).

The unfortunate thing is the gadget cost about $AU200! (Or was it $AU300? I can't remember, it was about 10 years ago.)

Peter

Answer:
The ace your mechanic had up his sleeve here, whether he knew it or not, was that many cars made for leaded fuel will run OK on unleaded with no modifications. If an engine has "soft" valve seats that rely on tetraethyl lead in the fuel for protective lubrication, then it'll probably need those valve seats replaced if you want it to last as long on unleaded. If you don't make the engine work hard, though, it's likely to last just fine anyway, and various old engines are quite tough enough in stock trim.

Newer leaded-fuel cars are very likely to have fully unleaded-compatible valve seats.

Exactly which cars came with which kind of valve seats varies enormously, and the way you drive makes a difference, too. I'm not sure what the exact deal is here in Australia. The USA started the switch to unleaded a long time before we did, though; the cutoff between soft and hard valve seats there was 1971!

(References here and here.)

The lead also acted as an octane booster, though, which means that you do have to make sure you're using unleaded fuel with a high enough octane rating, especially in sporty cars with higher compression ratios. If the octane rating's too low, you'll get detonation ("pinging" or "knocking"), which is very bad for the engine.

The magic tin widget doesn't, of course, do a thing to help with that either.

 

Charge!

Our school recently got involved in a robotics competition and while debating types of batteries to use to power our robot, laptop batteries seemed to be just about right as far as weight, voltage, and mAh ratings.

I was able to get a couple of Sony PCGA-BP2NZ 14.8v 4000mAh Li-ion batteries donated to us. The primary problem is how we get these beasts charged. Being electrical engineering students, we are somewhat electronically adept, and are not adverse to putting some effort into getting a charger built. Any ideas whether this would even be feasible or worth the trouble? Do laptops have a separate circuit board in them that handles charging that we could buy and modify if needed? We've already looked into external chargers; Sony doesn't make any and we couldn't find third party chargers for this model of battery.

Luke

Answer:
If you were regular Joes with only a rudimentary idea about which end of a soldering iron you're meant to hold, I'd strongly recommend against trying to make your own lithium ion charger. As you probably know, LiI batteries have no sense of humour at all about overcharging, and will drop dead or catch fire if mistreated.

The numbers are pretty simple, I think; keep the charge current moderate (if you want to be conservative, no more than one amp for your 4Ah pack; I don't know its exact specs) and clamp the maximum voltage HARD; your 14.8V pack's charge MUST terminate at 16.8 volts. Sixteen point eight zero, not sixteen point eight zero zero five.

I also know of one off-the-shelf charger that might suit you - the Maha C777 Plus.

 

BANG!

I thought you'd find this interesting, if you haven't run across it before.

"The art of shrinking coins using copper coils, magnetic fields and enough energy to power a small city."

Severian

Answer:
I hadn't read that particular article, but I've been resisting the urge to buy something from Bert's eBay store for some time!

[Eventually, the temptation became too much.]

 

Questionathon

Have you considered bolting an EDF unit on a big heat sink to see how ridiculous air cooling can go?

Also, whatever happened to the "coming soon" variants of the TMD fan? I still can't find anybody stocking 60mm or 80mm versions of it, and the only time I see the 70mm version is when it is bundled with a CPU heat sink. (I'm in the USA, in case that matters.)

I want TMD fans because I'm a sucker for novel unconventional designs. (I'm saving up to buy an RX-8...)

2) Brushless motors have been used in computer equipment for a long time. They've been available for RC aircraft for a while, too. But only recently (in the last year?) have Novak and Orion made brushless motors available for 1/10th scale electric RC cars. (In the USA, at least.) Do you happen to know why? I'm guessing it's related to the current draw involved, but I don't know where to find a definitive answer.

2.1) Possibly related to the above: Brushed motors give "braking" when you short the terminals together. Does a brushless motor work the same way?

3) One of my other hobbies is building plastic scale models of aircraft. I've successfully used LEDs for navigation lights and simulated strobes, but I'm at a loss as to the position lights. (They're the long green lights visible on the nose and vertical stabilizer of this F-18.)

Some Google-ing found this site, and I'll be experimenting with electroluminescent material. Since you've played with all kinds of related stuff, I want to ask if you know of anything that will work better than EL for this purpose. I want something like EL, but I care more about attributes like it being easy to cut and shape, easy to drive via thin wires (can't run 12-gauge wires inside an aircraft model), and not vulnerable to the kind of chemicals present in a hobby environment. (CA glue, MEK, Toluene, paint fumes, etc.)

Roger

Answer:
Regarding the ducted fan unit - why duct it? Why not just use an Aveox brushless spinning an 18 inch prop from 36 cells?

But seriously, folks - this sort of thing will only work slightly better than a garden variety noisy 60mm 12V fan, because there are serious diminishing return problems when you're cooling with air at ambient temperature. A better idea is to feed the computer chilled air, creating its own little server room, as it were. This idea's been reinvented over and over, usually with a portable or window-mount air conditioner as the cold air source and ordinary HVAC ducting to get the air to the PC.

More practically, the same ducting can be used to pipe hot air from PCs (or rack cabinets) outside.

Actually, you can buy TMD fans separately in the States - from here, for instance.

Regarding non-70mm TMD fans - it beats me why they haven't arrived. Presumably the fact that the TMD fan, despite its coolness, doesn't actually work significantly better than conventional designs, while it no doubt costs considerably more to make, means there's been no real demand for it.

I've also heard of a TMD fan defect in which the controller goes berserk and spools the fan up to Ludicrous Speed, which can cause the heavy rim of the impeller to disintegrate. I've never witnessed this entertaining failure mode myself, though.

There've been Aveox brushless motors and controllers that're suitable for cars (which is to say, relatively small and with relatively high RPM per input volt) for ages, since before the current sensorless designs - Aveox's RC7 was the first one. You could adapt the longer-can, lower RPM-per-volt Aveoxes for car use as well, provided you could get a big enough pinion and a small enough spur.

Trust me, I know.

Brushless motors haven't taken off in the R/C hobby in general mainly because they're really expensive. Prices have no doubt been coming down lately, but even an exotic hand-wound ultra-magnetted modified brush motor and super-zooty Japanese speed controller to match is cheap compared with a brushless solution with similar power.

Brushless is more efficient and needs less maintenance, of course, but given all the other bits of R/C racing cars that need replacement after every slapping of the boards, a bit of brush changing and commutator cleaning doesn't add that much to the workload.

(A reader's also pointed out that ROAR, IFMAR and NORRCA don't allow brushless cars to race in their various leagues. This is partly to keep running costs down, but mainly because if they did, all of the pro racers and all of the wannabes would immediately stop buying brush motors, and the brush motor companies would hire people to break the racing federations' knees. Don't expect this situation to change in the near future.)

Brushless motors can brake much the same as brushed ones; it depends on how the controller works. Most brushless motor/controller combinations let you drive a different way, though, because the motor will aggressively attempt to spin at the speed you ask for, not just coast if the car's rolling faster than the new throttle setting requests.

For your plane lighting, you might like to explore light guides - glue an LED into one end of a stick of clear acrylic, and frost the outside with sandpaper wherever you want it to glow. Here's an example.

 

Steampunk

Some time ago, you wrote that you've got a model steam engine quite a while ago. Any chance of an article about that, mayhaps? Or some pictures, possibly even a small mpeg? I'm a sucker for mechanical things that work as visibly as a steam engine. It's a sad affliction and one that medical science still has to find a non-terminal cure for...

Tom

Answer:
Sorry - don't hold your breath for a review.

The steam engine I've got isn't very exciting, anyway; it's a simple little single-action single-cylinder unit, which illustrates the principle and can be spun up to Ludicrous Speed if you take advantage of the fact that the boiler pressure release valve mounting hole neatly matches the nozzle of a butane refill can.

Note that a model engine running on boiling butane pressure should NOT have its alcohol burner lit.

There are lots of scale steam resources on the Web, as you might expect:

Steam Engines - A Gallery
e-Zee (Little) Steam Engines
Jensen Steam Engines
Stuart Models
Historic Steam Models
Steamco Engines Australia

...and on it goes.

You can spend a whole lot of money on these things - and that's even before you start pricing Stirling engines!

If you want to ask me a question, feel free - but please read this and this first.

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